By focussing a laser beam on a metal, a melt pool can be created. At a sufficiently high power density a keyhole or channel is created in the material running through the entire thickness of the components to be welded. By moving the laser beam with respect to the component, new material melts at the front of the keyhole and material solidifies at the rear thus creating the weld.
Shielding gas prevents the metal from oxidation. Laser welding can be performed without the addition of filler wire to the melt pool (autogeneous welding), or with addition of filler wire to the melt pool (heterogeneous welding). The latter may be done, e.g., to fill the gap or optimise the weld metal composition.
With laser welding, continuous joints can be produced at high speed. Other advantages are the low heat input compared to other welding processes, resulting in a narrow weld and small heat affected zone.